Technical Field
The present invention relates to an engine starter unit.
Related Art
Conventionally, as a method for starting an engine, after the engine is rotated at low-speed by a pinion-moving type starter which moves a pinion to an engagement position with a ring gear, fuel is injected into a combustion chamber, thereby speeding the engine up to an idling speed.
However, in this method, the engine is speeded up from the low-speed range (400 rpm or less) to the idling-speed by only combustion, which causes poor fuel efficiency. There is a need for a technique which can improve fuel efficiency by speeding the engine up to the idling-speed before fuel is injected.
As methods for speeding the engine up to the idling-speed before the injection of the fuel, there are a method for starting the engine using a motor and generator, a so-called ISG (integrated starter generator), and a method for starting the engine using an MG (motor generator).
However, there is a problem that ISGs or MGs are expensive. Further, they are alternating-current machines, accordingly they have poor start-up performance, compared with the pinion-moving type starter including a direct-current motor.
On the other hand, the applicant has suggested a high-speed cranking starter unit (JP2013-261092, which is not published) as a technique for cranking the engine up to a high-speed range using the pinion-moving type starter including the direct-current motor.
The high-speed cranking starter unit uses a starter including a direct-current motor having performance capable of cranking the engine up to the high-speed range of 450 rpm or more. The starter cranks the engine up to a given speed of 450 rpm or more in a predetermined duration Ta, and the starter is turned OFF before ignition. The predetermined duration Ta is set short, thereby the user is less likely to feel the cranking noise to be noisy.
However, in the high-speed cranking starter unit, since the cranking time is short, it might be difficult for the driver (the user) to recognize by sounds whether or not the engine has started. Since the engine is cranked up to the high-speed range in a short period, the cranking noise in the high-speed cranking starter unit is different from the conventional cranking noise when the engine is cranked up to the low-speed range. Accordingly, the user might be unlikely to recognize the noise as the cranking noise. In this case, it is difficult to recognize by sound whether the engine is normally cranked.
Although the engine has already started, the user might misguidedly believe the engine has not started yet and turn an ignition switch again during starting triggered by a first ON operation of the ignition switch, i.e. when the engine has been started in response to firstly turning the ignition switch (referred to IG switch) ON by the user, or when the engine is restarted from an idling stop state.
Since cranking is performed at the high-speed range of 450 rpm or more, if the starter is driven triggered by reoperation of the IG switch when the engine has been started, the ring gear and pinion are worn or generate noise.
In PTL1 (Japanese patent publication No. 2008-128137), in an idling stop system, when a restart requirement is issued during speeding down of the engine, the starter is prevented from being driven until the engine speed lowers to a given speed or less. However, prohibiting the starter from being driven during starting triggered by the ON operation and the method therefor has not been disclosed. There is no disclosure of a problem specific to the starter unit that cranks the engine up to a given speed of 450 rpm or more, the problem being that the user cannot recognize whether the engine has started.